On the Mechanism of Magnesium Storage in Micro- and Nano-Particulate Tin Battery Electrodes

Abstract

This study reports on the electrochemical alloying-dealloying properties of Mg2Sn intermetallic compounds. 119Sn Mössbauer spectra of β-Sn powder, thermally alloyed cubic-Mg2Sn, and an intermediate MgSn nominal composition are used as references. The discharge of a Mg/micro-Sn half-cell led to significant changes in the spectra line shape, which is explained by a multiphase mechanism involving the coexistence of c-Mg2Sn, distorted Mg2−δSn, and Mg-doped β-Sn. Capacities and capacity retention were improved by using nanoparticulate tin electrodes. This material reduces significantly the diffusion lengths for magnesium and contains surface SnO and SnO2, which are partially electroactive. The half-cell potentials were suitable to be combined versus the MgMn2O4 cathodes. Energy density and cycling properties of the resulting full Mg-ion cells are also scrutinized.

Alloy Anode Materials for Rechargeable Mg Ion Batteries

“…The anions present in APC such as Ph 4 Al − , Ph 2 AlCl 2 − , PhAlCl 3 − , and AlCl 4 − are susceptible to extract Mg from Mg metal and Mg 2 Sn alloys through galvanic replacement reactions. Nacimiento et al [ 143 ] have investigated the storage behaviors of Mg in micro‐ and nanoparticulate Sn electrodes. The Sn electrodes (80 wt% micro‐ or nano‐Sn, 10 wt% carbon black, and 10 wt% binder) were evaluated in half‐cell configuration versus Mg metal in 0.5 м PhMgCl/THF or 0.5 м EtMgCl/THF electrolyte solutions.…”

“…In recent years, the pioneers devoting to alloy anodes have constructed several promising MIB prototypes. These include Sn anode‐1 м Mg(ClO 4 ) 2 /AN electrolyte solution‐Mg x V 2 O 5 cathode, [ 36b ] Mg 2 Sn anode‐0.5 м Mg(TFSI) 2 /diglyme, 0.5 м Mg(TFSI) 2 /PC or 1 м Mg(ClO 4 ) 2 /AN electrolyte solution–V 2 O 5 oxide cathode, [ 137 ] nano Sn anode–0.5 м Mg(ClO 4 ) 2 /AN electrolyte solution–MgMn 2 O 4 spinel cathode, [ 143 ] Mg 3 Bi 2 anode–1 м LiTFSI and 2 м Mg(TFSI) 2 /AN electrolyte solution‐Prussian blue (PB) cathode [ 160 ] and Mg 3 Bi 2 anode–1 м Mg(TFSI) 2 /DME electrolyte solution–S cathode [ 177 ] ) systems as important examples. Theoretical and actual energy densities (Wh Kg −1 ) of promising full MIBs based on alloy anodes have been estimated and compared in Table 1 .…”

“…This full cell prototype could deliver an initial reversible capacity of 150 mAh g −1 (based on the loading of the cathode) and maintained a stable specific capacity around 120 mAh g −1 after 50 cycles (Figure 18c). In a follow‐up work, [ 143 ] full cells consisting of nano‐Sn anode, MgMn 2 O 4 cathode, and 0.5 м Mg(ClO 4 ) 2 /AN electrolyte solution were tested in Swagelok‐type three‐electrode cells versus a Mg metal reference electrode. The Mg ion full cell is workable and delivers a specific capacity of 150 mAh g −1 (based on the loading of the cathode) and the energy density of this MIB prototype was calculated up to 120 Wh kg −1 .…”

Recent Progress and Challenges in the Optimization of Electrode Materials for Rechargeable Magnesium Batteries

“…Some groups have also conducted the optimization of Mg metal by minimizing the particle size to achieve better performance. [ 33 ] Other anodes such as nanostructured Sn, [ 84,85 ] SnSb alloys, [ 86,87 ] Bi, [ 88–90 ] Bi‐based composite, [ 91 ] and size‐controlled Li 4 Ti 5 O 12 [ 92 ] were also reported.…”

“…Some groups have also conducted the optimization of Mg metal by minimizing the particle size to achieve better performance. [33] Other anodes such as nanostructured Sn, [84,85] SnSb alloys, [86,87] Bi, [88][89][90] Bi-based composite, [91] and size-controlled Li 4 Ti 5 O 12 [92] were also reported. All these reported electrode materials are far from practical applications due to the low voltage, specific capacity, and especially the sluggish Mg 2+ kinetics.…”